1. Field of the Invention
The invention relates to an energy monitoring device, and particularly for monitoring the energy of an excimer or molecular fluorine laser emitting below 200 nm.
2. Discussion of the Related Art
In the past, i.e., prior to the investigations leading up to the present application, very little was known about the behavior of UV-photodetectors under long-term laser pulse radiation exposure below 200 nm. Only a limited number of CW synchrotron exposure experiments had been done at Physikalisch-Technische Bundesanstalt, Berlin (PTB) and the National Institute of Standards and Technology (NIST).
Until now, no reliable energy monitor for detecting the pulse energy of e.g. a molecular fluorine (F2) laser emitting around 157 nm has been available.
For detecting 193 nm and 248 nm excimer laser radiation, UV-photodetectors such as the International Radiation Detectors, Inc. (IRD) UVG 100 or the Hamamatsu S 5226, or S1226 have been used typically as energy monitor detectors. However, these detectors strongly degrade under 157 nm laser exposure.
It is therefore desired to have a reliable photodetector for monitoring pulse energies and/or another parameter of an excimer or molecular fluorine laser beam.